Flashback Blood Collection Needle

ABSTRACT

A needle assembly includes a transparent or translucent housing with a fluid inlet and outlet end, a flashback chamber, and a venting mechanism therebetween. The venting mechanism includes a blocking member to control the fluid flow in the venting mechanism so that it flows along the longest path through the vent. Substantially axially aligned inlet and outlet cannulas extend from the housing and communicate with the chamber. A sealable sleeve covers the external end of the outlet cannula. Relative volumes of the cannulas, the chamber, and the sleeve are selected to provide rapid reliable flashback indicative of venous entry with an internal vent positioned within the housing to divide the interior into first and second chambers, with the second chamber being adapted to maintain a negative pressure therein relative to the external environment so as to inhibit leakage of blood from the needle tip on withdrawal from the patient.

The present application is a Divisional application of U.S. applicationSer. No. 13/018,740, entitled “Flashback Blood Collection Needle”, filedFeb. 1, 2011, which is a Continuation-in-Part application based uponU.S. application Ser. No. 12/206,273, filed Sep. 8, 2008, entitled“Flashback Blood Collection Needle” which is a Continuation-in-Partapplication based upon U.S. application Ser. No. 12/044,354, now U.S.Pat. No. 7,766,879, filed on Mar. 7, 2008, also entitled “FlashbackBlood Collection Needle”, the entire disclosures of each of which areherein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a device for collecting blood samplesby performing venipuncture on a patient. More particularly, the presentinvention relates to a needle assembly for multiple sample bloodcollection that allows a phlebotomist to determine whether vein entryhas occurred when collecting a blood sample from a patient into anevacuated blood collection tube.

2. Description of Related Art

Venipuncture is the primary method used for acquiring blood samples forlaboratory testing. In performing venipuncture procedures, aphlebotomist must follow several steps simultaneously. Such stepsinclude assessing the patient's overall physical and psychologicalcondition so as to properly select a venipuncture site and technique.The phlebotomist must also select the proper corresponding equipment,perform the technique so as to control bleeding, and properly collectand identify fluid specimens for testing. The phlebotomist mustascertain all of these coinciding factors, as such factors may adverselyaffect the distension of the vein and the length of the venipunctureprocedure.

Various venipuncture devices have been developed to address theabove-described problems. These devices include products intended toassist the phlebotomist in confirming that vein entry has been made seee.g., U.S.. Pat. Nos. 5,222,502 and 5,303,713. Such a device contains aneedle assembly with a housing that defines a chamber therein. A singlecannula pointed at both ends is affixed to the housing. The intravenous(IV) end of the cannula is adapted for penetration of a patient's vein.The non-patient end of the cannula has a sealable sleeve and is adaptedfor penetration of a penetrable stopper positioned within an evacuatedcontainer.

Upon vein entry with the intravenous end of the cannula, blood will flowthrough the cannula, into the sealable sleeve and into the housingchamber, which is clear or translucent for visualization (“flashback”).Once air is vented from the flashback chamber, the blood therein ispressurized each time the sealable sleeve is pushed toward the housingchamber upon activation of an evacuated container.

Due to the length of time between vein entry and flashback, thephlebotomist may erroneously believe that satisfactory vein entry hasnot been achieved since there is no immediate indication of vein entryin the see-through chamber. The phlebotomist may unnecessarily repeatthe venipuncture procedure, requiring replacement of the evacuatedcontainer and/or the needle assembly itself. Such a repetitive processprolongs the physical and emotional discomfort endured by the patient.In such cases, a phlebotomist may use a blood collection set to providesome entry indication, and will then incur the cost of the bloodcollection set, as well as the cost of a discard tube.

It would therefore be desirable to provide an improved blood collectiondevice that permits blood flow through a relatively short flow pathdirectly into a flashback chamber, thereby providing immediateindication of successful vein entry.

SUMMARY OF THE INVENTION

The invention provides a needle assembly for the extraction of at leastone fluid sample into an evacuated container for laboratory testing. Theneedle assembly provides a clear or translucent housing with sufficientdead space for blood to flow into a flashback chamber for visualizationby the user to confirm successful vein entry, with an internal ventmechanism.

In one embodiment, the invention relates to a needle assembly comprisinga housing defining a housing interior, a cannula having a patientpuncture tip extending from a first end of the housing, and anon-patient puncture tip extending from a second end of the housing. Thenon-patient puncture tip and the patient puncture tip are in fluidcommunication with each other through the cannula, such that the solecommunication path between the housing interior and the externalenvironment is via the patient puncture tip. A porous vent is positionedwithin the housing interior to separate the housing interior into afirst chamber and a second chamber, with the cannula being in fluidcommunication with the first chamber. The porous vent includes pores forpassage of blood therethrough from the first chamber to the secondchamber. The first chamber and the second chamber are configured suchthat upon insertion of the patient needle tip into a patient, bloodflows through the cannula and into the first chamber without sealing theporous vent. At this point in the process, the blood “flashback” can bevisualized in the first chamber. Upon application of an evacuatedcontainer to the non-patient puncture tip, blood is drawn from the firstchamber and air is drawn from the second chamber, thereby establishing anegative pressure within the second chamber with respect to an externalenvironment of the needle assembly. Blood can thereafter be drawn intothe first chamber and through the porous vent, with a negative pressuremaintained in the second chamber.

In one embodiment, the cannula includes a first end comprising thepatient puncture tip and a second end comprising the non-patientpuncture tip, with an opening between the first end and the second endproviding fluid communication between the cannula and the first chamberof the housing. In an alternate embodiment, the cannula comprises afirst cannula having a patient puncture tip, with the needle assemblyfurther comprising a second cannula including the non-patient puncturetip, with the first cannula and the second cannula substantially axiallyaligned and separated by a gap in fluid communication with the firstchamber of the housing. A sleeve may also extend about the non-patientpuncture tip.

In one embodiment, the second chamber may include multiple interiorregions in fluid communication, such as a first interior region and asecond interior region. The first and second interior regions of thesecond chamber are in fluid communication with each other through theporous vent.

In a particular embodiment, the first end of the housing comprises anelongated longitudinal first portion having a first diameter and thesecond end of the housing comprises a second portion having a seconddiameter larger than the first diameter of the first portion. In such anembodiment, the porous vent may be positioned within the housinginterior between the first portion having a first diameter and thesecond portion having a second diameter. Alternatively, the porous ventmay be positioned within the housing interior at a location spanning thetransition between the first diameter of the first portion and thesecond diameter of the second portion. In embodiments where the secondchamber includes multiple interior regions, such as a first interiorregion and a second interior region, the first chamber may extend alonga portion of the longitudinal first portion, with at least one of theinterior regions, such as the second interior region of the secondchamber extending longitudinally concentrically about the first chamber.In this manner, the external diameter, and thus the external profile ofthe needle assembly, can be decreased.

In yet a further embodiment, a method of preventing leakage, such as,for example, blood droplets, at the patient puncture tip in a needleassembly is provided. The method involves receiving blood through apatient puncture tip and into a first chamber of a needle assembly, withthe needle assembly including a needle housing defining a housinginterior; a cannula having the patient puncture tip extending from afirst end of the needle housing; a non-patient puncture tip extendingfrom a second end of the needle housing, the non-patient puncture tipand the patient puncture tip being in fluid communication with eachother through the cannula; and a porous vent positioned within thehousing interior and separating the housing interior into a firstchamber and a second chamber. The cannula is in fluid communication withthe first chamber such that the sole communication path between thehousing interior and the external environment is via the patientpuncture tip, and the porous vent includes pores for passage of bloodtherethrough from the first chamber into the second chamber. Fluidcommunication is established between the non-patient puncture tip and anevacuated collection container, such that blood contained within thefirst chamber is drawn into the evacuated collection container and airis drawn out of the second chamber through the porous vent. As such, anegative pressure is established within the second chamber relative tothe external environment of the needle assembly, such that blood flowsthrough the cannula into the first chamber and contacts the porous vent.Blood is then drawn through the pores of the porous vent toward thesecond chamber such that after removing the patient puncture tip fromthe vasculature of the patient any blood contained within the cannula isdisplaced away from the patient puncture tip toward the second chamberbased upon the negative pressure established within the second chamber.

Additionally, a further step may include establishing fluidcommunication between the non-patient puncture tip and a secondevacuated collection container prior to drawing blood through thepatient puncture tip and through the cannula into the second evacuatedcollection container, followed by releasing the fluid communicationbetween the non-patient puncture tip and the second evacuated collectioncontainer.

In yet a further embodiment, the invention is directed to a method ofcollecting a sample of blood from a patient into an evacuated bloodcollection tube using a blood collection assembly having a patientneedle tip and a non-patient needle tip and a housing having a flashbackvisualization chamber. The method involves using a needle assemblycomprising a housing having a porous vent positioned therein to separatean interior of the housing into a first chamber forming the flashbackvisualization chamber and a second chamber, the first chamber and secondchamber being configured such that air is drawn out of the secondchamber through the porous vent and into the evacuated blood collectiontube along with the blood sample, thereby establishing a negativepressure within the second chamber. The negative pressure causes bloodto be drawn into the first chamber and contact the porous vent, suchthat after the patient needle tip is removed from the patient, thenegative pressure within the second chamber draws blood from the patientneedle tip toward the second chamber, thereby preventing leakage ofblood from the patient needle tip after removal from the patient.

In another embodiment, the invention is related to a needle assemblyhaving a housing defining a housing interior wherein the housingcomprises at least one cannula having a patient puncture tip extendingfrom a first end of the housing and a non-patient puncture tip extendingfrom a second end of the housing. The non-patient puncture tip and thepatient puncture tip are in fluid communication with each other withinthe housing interior. The assembly also includes a porous ventpositioned within the housing interior separating the housing interiorinto a first chamber and a second chamber within the housing interior.The porous vent includes pores for passage of fluid therethrough fromthe first chamber to the second chamber. The porous vent can comprise atubular member including an axial bore which surrounds at least aportion of the at least one cannula. A blocking member is locatedadjacent to or within the axial bore of the porous vent and controlsflow of the fluid through the vent such that the fluid flows along thelongest path through the porous vent. This longest path depends upon theshape of the porous vent. In one embodiment wherein the porous vent iscylindrically or tubular shaped having a longer length thancircumference, the flow can be in an axial direction along alongitudinal path through the porous vent. In another embodiment wherethe porous plug is washer shaped having a circumference which is greaterthan its length, the flow having the longest path can be in the radialdirection. The porous vent with the blocking member reduces oreliminates the amount of uncontrolled flow of fluid through the porousvent along the shortest path or the path of least resistance. The solecommunication path between the housing interior and the externalenvironment is via the patient puncture tip. The porous vent has a firstend face, a second end face, and a central portion extending between thefirst end face and the second end face. According to one embodiment, theporous vent is configured to cause the fluid to flow along a controlledlongitudinal path from the first end face to either the central portionor the second end face of the porous vent and subsequently through acentral opening between the first and the second chamber. This centralopening can be located adjacent to the central portion of the porousvent. According to another embodiment, the porous vent can be configuredto cause the fluid to flow along a controlled longitudinal path from thefirst end face to the second end face and subsequently into the secondchamber through either the first end face and/or the second end face.According to yet another embodiment, the porous vent can be washershaped having the first end face and the second end face blocked tocause the fluid to flow along a controlled radial path from an innerportion of the porous vent to the outer circumferential end face of theporous vent and into the second chamber.

The blocking member is configured to block at least a portion of theporous vent to render this portion of the vent non-porous to control theflow of fluid therethrough. The blocking member can block at least aportion of an inside surface of the axial hole surrounding at least aportion of the cannula. According to one embodiment, the blocking membercomprises a non-porous bushing press-fitted into the inside surface ofthe porous vent. This bushing can comprise steel or any other type ofmetal cannula, an extruded plastic tube, a tubular molded part, and thelike. The bushing can have a length that is substantially equal to alength of the porous vent. According to another embodiment, the blockingmember can comprise an adhesive or sealant located in a space between aninside surface of the porous vent and an outer diameter of the cannula.According to another embodiment, the back end surface of the porousmember can be blocked with an adhesive material to control the flow offluid through the porous vent. According to yet another embodiment, theblocking member can be formed by melting or fusing the inner diametersurface portion of the porous vent. According to another embodiment, theblocking member can be a separate member, such as a plastic tubular orcylindrical member that is placed in abutting relationship with respectto the inside surface of the porous vent. This cylindrical member canextend from a portion of the housing.

According to one design, the at least one cannula can comprise a singlecannula extending through the housing. The single cannula can include alumen extending therethrough, a first end comprising the patientpuncture tip, a second end comprising the non-patient puncture tip, andan opening through the cannula into the lumen at a location between thefirst end and the second end providing fluid communication between thelumen of the cannula and the first chamber of the housing. According toanother embodiment, the at least one cannula can comprise a firstcannula extending from the housing and comprising the patient puncturetip, and a second cannula extending from the housing and comprising thenon-patient puncture tip. The first cannula and the second cannula aresubstantially axially aligned within the housing interior and separatedfrom each other by a gap in fluid communication with the first chamberof the housing. The first chamber and the second chamber are configuredsuch that upon insertion of the patient puncture tip into a patientcauses blood to flow into the first chamber without sealing the porousvent, and upon application of a negative pressure source to thenon-patient puncture tip, blood and air are drawn from the first chamberand air is drawn from the second chamber, thereby establishing anegative pressure within the second chamber with respect to an externalenvironment of the needle assembly. Upon removal of the patient puncturetip from the patient, the negative pressure within the second chamberdraws blood from the patient needle tip toward the second chamber toprevent blood droplets from being present at the patient puncture tip.

In yet another embodiment, the invention relates to a needle assemblycomprising a housing defining a housing interior. The housing comprisesat least one cannula having a patient puncture tip extending from afirst end of the housing and a non-patient puncture tip extending from asecond end of the housing. The non-patient puncture tip and the patientpuncture tip are in fluid communication with each other within thehousing interior. A porous vent is positioned within the housinginterior to separate the housing interior into a first chamber and asecond chamber. The porous vent includes pores for passage of fluidtherethrough from the first chamber to the second chamber. The porousvent is configured to control flow of the fluid such that the fluidflows along the longest path therethrough. The needle assembly isdesigned such that the sole communication path between the housinginterior and the external environment is via the patient puncture tipand the first end of the housing comprises an elongate longitudinalfirst portion having a first diameter and the second end of the housingcomprises a second portion having a second diameter larger than thefirst diameter of the first portion. The porous vent is positionedwithin the housing interior between the first portion having a firstdiameter and the second portion having a second diameter at a locationspanning a transition point between the first diameter of the firstportion and the second diameter of the second portion. The porous ventcan comprise a tubular member having a first end face, a second endface, and a central portion located between the first end face and thesecond end face. The tubular member further includes an axial holeconfigured for surrounding at least a portion of the cannula. The axialhole defines an inside surface of the porous vent and the assemblyfurther includes a blocking member at the inside surface of the axialhole for blocking at least a portion of the porous vent to render thisportion of the vent non-porous to cause the fluid to flow along acontrolled longitudinal path from the first end face to either thecentral location or the second end face and subsequently through acentral aperture opening between the first chamber and the secondchamber. The blocking member can be a non-porous bushing press-fittedinto the inside surface of the porous vent or an adhesive locatedbetween an inside surface of the porous vent and an outer diameter ofthe cannula. Alternatively, the inside portion of the porous vent can berendered non-porous by fusing this inner surface portion of the porousvent. According to another embodiment, the blocking member can be aseparate member, such as a plastic tubular or cylindrical member that isplaced in abutting relationship with respect to the inside surface ofthe porous vent. This cylindrical member can extend from a portion ofthe housing.

In another embodiment, the invention relates to a needle assemblycomprising a housing defining a housing interior. The housing comprisesat least one cannula having a patient puncture tip extending from afirst end of the housing and a non-patient puncture tip extending from asecond end of the housing. The non-patient puncture tip and the patientpuncture tip are in fluid communication with each other within thehousing interior. A porous vent is positioned within the housinginterior separating the housing interior into a first chamber and asecond chamber. The porous vent includes pores for passage of fluidtherethrough from the first chamber to the second chamber. The porousvent is configured to control flow of the fluid such that the fluidflows in an axial direction therethrough. The housing includes a rearhub which can block a back end face of the porous vent. Alternatively,the rear hub can leave a portion of the second end face exposed. Therear hub includes a cylindrical portion extending therefrom. Thiscylindrical portion extends into the first chamber toward the first endof the housing to define a portion of the first chamber. The needleassembly is designed such that the sole communication path between thehousing interior and the external environment is via the patientpuncture tip. The porous vent comprises a tubular member having a firstend face, a second end face, and a central portion extending between thefirst end face and the second end face. The tubular member furtherincludes an axial hole configured for surrounding at least a portion ofthe cylindrical portion extending from the rear hub. The at least onecannula is located within at least a portion of the cylindrical portion.The cylindrical portion extending from the rear hub into the axial holeof the porous vent abuts against the inside surface of the porous ventto act as a blocking member to render a portion of the vent non-porousand to cause the fluid to flow along a controlled longitudinal path andconsequently through either a central aperture opening between the firstand the second chamber or through either the first end face or thesecond end face of the porous vent. An adhesive can be located betweenan inside surface of the porous vent and an outer diameter of thecannula and/or the cylindrical portion or the inner surface portion ofthe porous vent can be fused to render this portion non-porous in orderto assist in controlling the flow of fluid through the porous vent.

According to still another embodiment, the invention relates to a methodof preventing leakage of a blood droplet from a patient puncture tip ofa needle assembly. The method includes: a) receiving blood through apatient puncture tip and into a first chamber of a needle assembly, theneedle assembly comprising: i) a needle housing defining a housinginterior, the housing comprising at least one cannula having a patientpuncture tip extending from a first end of the housing and a non-patientpuncture tip extending from a second end of the housing; and ii) aporous vent positioned within the housing interior and separating thehousing interior into a first chamber and a second chamber, with thenon-patient puncture tip and the patient puncture tip being in fluidcommunication with each other within the first chamber such that thesole communication path between the housing interior and the externalenvironment is via the patient puncture tip. The porous vent includespores for passage of blood and air therethrough from the first chamberinto the second chamber and the porous vent is configured to controlflow of the blood and air such that the blood and air flows along thelongest path therethrough. The method further includes: b) establishingfluid communication between the non-patient puncture tip and a negativepressure source such that blood contained within the first chamber isdrawn out of the non-patient puncture tip and air is drawn out of thesecond chamber through the porous vent, thereby establishing a negativepressure within the second chamber relative to the external environmentof the needle assembly such that blood flows through the cannula intothe first chamber and contacts the porous vent; and c) drawing blood andair through the pores of the porous vent toward the second chamber basedupon the negative pressure established within the second chamber suchthat blood contained within a lumen of the patient puncture tip isdisplaced away from the patient puncture tip and toward the secondchamber. The method is such that the receiving step a) comprisesreceiving blood through the lumen of the patient puncture tip from apatient's bloodstream, and the drawing step c) displaces blood away fromthe patient puncture tip after removing the patient puncture tip fromthe source of blood, such as, for example, from the vein. The methodfurther includes the step that after step b) and prior to step c),releasing the fluid communication between the non-patient puncture tipand the negative pressure source. The porous vent can comprise a tubularmember having a first end face and a second end face and wherein thetubular member further includes an axial hole configured for surroundingat least a portion of the cannula. The method includes rendering theinside surface of the axial hole non-porous to cause the fluid to flowalong the longest path through the porous vent and subsequently into thesecond chamber. Depending upon the shape of the porous vent, thislongest path can be a longitudinal path or a radial path. A blockingmember can be provided to render the inside surface of the axial holenon-porous. This blocking member can be a bushing formed from anon-porous metal or plastic material press-fitted into the insidesurface of the porous vent, an adhesive located between an insidesurface of the porous vent and an outer diameter of the cannula, a fusedinner surface portion of the porous vent, and/or a separate member thatis placed in an abutting relationship with respect to the inside surfaceof the porous vent.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a typical embodiment of the needleassembly of the present invention.

FIG. 2 is a cross-sectional view of a second embodiment.

FIG. 3 is a cross-sectional view of a third embodiment.

FIG. 4 is a cross-sectional view of a fourth embodiment.

FIG. 5 is a schematic view of the needle assembly of FIG. 1 prior touse.

FIG. 6 is a schematic view similar to FIG. 5, but showing the first signof venous entry.

FIG. 7 is a schematic view of a fifth embodiment.

FIG. 8 is a perspective view of a needle assembly having a flash chamberin a further embodiment.

FIG. 9 is a rear perspective view of the needle assembly having a flashchamber of FIG. 8.

FIG. 10 is an exploded view of the needle assembly having a flashchamber of FIG. 8.

FIG. 11A is a cross-sectional view of the needle assembly having a flashchamber of FIG. 8.

FIG. 11B is an enlarged cross-sectional view of a portion of the needleassembly of FIG. 11A.

FIG. 12A is a cross-sectional view of a needle assembly having a flashchamber used in connection with a blood collection assembly in yet afurther embodiment.

FIG. 12B is an enlarged sectional view of a portion of the needleassembly of FIG. 12A.

FIG. 13A is a cross-sectional view of a needle assembly having a flashchamber used in connection with a blood collection assembly in yet afurther embodiment.

FIG. 13B is an enlarged sectional view of a portion of the needleassembly of FIG. 13A.

FIG. 13C is an enlarged sectional view of a portion of the needleassembly of FIG. 13B.

FIG. 14 is a perspective view of the needle assembly of FIG. 13A shownin combination with a blood collection holder, with a needle shield in ashielding position.

FIG. 15 is a side view of the needle assembly of FIG. 14.

FIG. 16 is an enlarged side sectional view of the needle assembly ofFIG. 15 without the cannula.

FIG. 17 shows a cross-sectional view of the needle assembly of theinvention, without the cannula, according to one design including ablocking member located within the porous vent.

FIG. 18 shows a perspective view of the porous vent shown in FIG. 17.

FIG. 19 shows a cross-section view of the porous vent taken along lineXIX-XIX of FIG. 18.

FIG. 20 is a cross-sectional view of the needle assembly using a porousvent without a blocking member showing the uncontrolled radial flow offluid along the shortest path through the porous member.

FIG. 21 is a cross-sectional view of the needle assembly of theinvention including the blocking member of the invention and showing oneembodiment of the controlled flow of fluid along the longest paththrough the porous vent wherein the longest path is in the longitudinaldirection.

FIG. 22A shows a cross-sectional view of the needle assembly accordingto an alternative design of the invention.

FIG. 22B shows a cross-sectional view of the needle assembly accordingto another design of the invention.

FIG. 22C shows a cross-sectional view of the needle assembly accordingto yet another design of the invention.

FIG. 22D shows a cross-sectional view of the needle assembly accordingto still another design of the invention.

FIG. 23A shows a cross-sectional perspective view of the needle assemblyof the invention according to another design.

FIG. 23B shows a close-up cross-sectional perspective view of the porousvent and chamber arrangements of FIG. 23A.

FIG. 24 shows a cross-sectional view of the needle assembly of theinvention according to another design.

FIG. 25 is a cross-sectional view of the needle assembly of theinvention including the blocking member of the invention and showinganother embodiment of the controlled flow of fluid along the longestpath through the porous vent wherein the longest path is in a radialdirection.

DETAILED DESCRIPTION

An embodiment of the invention provides a needle assembly for bloodcollection that provides a visual indication of vein entry (“flashback”)upon collection of a blood or other fluid sample from a patient into oneor more evacuated blood collection tubes and inhibits leakage of theblood or fluid sample from the IV cannula on removal from the patient.

Various embodiments of the present invention are shown in the FIGS. Withreference to FIGS. 1-6, this embodiment is directed to a needle assembly210 with a housing 212 having a fluid inlet end 214, a fluid outlet end216 and a frustum-shaped exterior wall 218 extending between the ends.Exterior wall 218 defines the housing interior 220. Housing 212 furtherincludes a cylindrical interior wall 224 that extends in the housinginterior 220 from fluid inlet end 214 substantially concentrically withcylindrical exterior wall 218 to a vent plug 900. Cylindrical interiorwall 224 and vent plug 900 define a flashback chamber 226.

Needle assembly 210 also includes a fluid inlet cannula 236 having anexterior end that defines a sharpened bevel and an interior end 244 thatis mounted fixedly in fluid inlet end 214 of housing 212. Fluid inletcannula 236 is characterized further by a substantially cylindricallumen extending between the ends and communicating with the interior ofhousing 212.

Needle assembly 210 further includes a fluid outlet cannula 252. Withreference to FIGS. 5-6, outlet cannula 252 concludes a blunt interiorend 254, an exterior end defining a sharpened bevel and a substantiallycylindrical lumen extending between the ends. Portions of outlet cannula252 between the ends are securely affixed in outlet end 216 of housing212. Outlet cannula 252 is mounted so that interior end 254 passessubstantially coaxially into interior wall 224 and so that interior end254 of outlet cannula 252 substantially aligns axially with interior end244 of inlet cannula 236. Additionally, interior end 254 of outletcannula 252 is spaced only a small distance from interior end 244 ofinlet cannula 236. An axial gap between interior end 254 of outletcannula 252 and interior end 244 of inlet cannula 236 that is less than0.5 mm may result in a flashback that is inconsistent.

Cylindrical interior wall 224 is dimensioned relative to outlet cannula252 to achieve both desirable flow of blood through assembly 210 and toachieve effective flashback indication. In particular, cylindricalinterior wall 224 preferably is dimensioned to provide a radial gaparound outlet cannula 252 of about 0.2 mm, as indicated by dimension “c”in FIG. 1. This gap achieves a substantially laminar blood flow withinflashback chamber 226 and prevents blood hemolysis. Additionally, thesmall radial gap between cylindrical inner wall 224 and outlet cannula252 enables a drop of blood to be spread thinly across the radial gap inflashback chamber 226 to provide a magnified flashback indication with avery small volume of blood. Thus, an easily visualized flashbackindication is achieved quickly at the first appearance of blood frominterior end 244 of inlet cannula 236.

Needle assembly 210 further includes a sealable sleeve 261 mounted tofluid outlet end 216 of housing 212 and covering exterior end 258 ofoutlet cannula 252 when sealable sleeve 261 is in an unbiased condition.However, sealable sleeve 261 can be collapsed in response to pressureexerted by the stopper of an evacuated tube for urging exterior end 260of outlet cannula 252 through both sealable sleeve 261 and stopper of anevacuated tube, as known in the art.

The above embodiment is described in terms of a vent plug. However, anyvent mechanism is suitable. The vent mechanism may be, for example, aporous vent plug formed from a matrix or carrier material, typicallyhydrophobic, that is coated with, impregnated with, or otherwise,contains a hydrophilic material that swells on contact with aqueous orwater containing substances. The hydrophobic carrier material can be butis not limited too, high-density polyethylene, polytetrafluoroethylene,ultra-high molecular weight polyethylene, Nylon 6, polypropylene,polyvinylidine fluoride and polyethersulfone. The swellable nature ofthe hydrophilic material thereby provides the sealing function in thevent upon contact with blood. It is also possible to use a porous ventplug that becomes sealed upon contact with blood using biologicalphenomena, e.g., by clotting and/or cell agglutination that blocks thevent; a superabsorbant material to seal the vent by swelling on contactwith an aqueous fluid; a porous vent configured to form a tortuous pathfor fluid movement therethrough; or a one-way valve, (e.g., a thin flapsuch as plastic film covering a vent, a deformable seal such as a rubberor plastic duckbill valve, or a deformable wrap over a vent). It shouldbe noted that any combination of these various mechanisms is alsopossible.

FIGS. 2-4 show embodiments with varying vent plugs. FIG. 2 shows a ventplug 900 a, which is located at the end of the cylindrical inner wall224 a and fitted into a recess 301 in the housing interior non-patientwall 300. FIG. 3 shows a vent plug in a similar location to that of FIG.2, however, vent plug 900 b has a shoulder 901 b. FIG. 4 shows a ventplug 900 c that is located both within the cylindrical inner wall 224 cand the recess 301 in the housing interior non-patient wall 300, and hasa shoulder 901 c. The vent plug location in each of these embodiments issuch that no air can flow out of the flashback chamber 226 into thehousing interior 220 without passing through the vent mechanism (900 a,b, c).

FIGS. 5 and 6 provide schematic representations of the needle assembly210 of FIG. 1 before and after a conventional venipuncture, in which,the needle assembly 210 is connected to a holder (not shown) andpunctures the patient's skin to make a vein entry. Upon vein entry,blood enters the IV cannula 236 and flows toward the flashback chamber226. The blood flows from inlet cannula 236 into the space between inletand outlet cannula, such that blood flows both into the outlet cannula252 and into flashback chamber 226. At this point in time, flashbackchamber 226, indicates successful vein entry and reduces the volume ofair present in housing 212 shown in FIG. 6. Air that was at atmosphericpressure within the lumen of the IV cannula 248, flashback chamber 226,housing interior 220, and the lumen of the non-patient cannula 262 priorto vein entry, thus experiences compression due to the influence ofvenous pressure and this air is therefore forced through the IV cannula236 shown in FIG. 6 into the flashback chamber 226 and through the ventplug 900 into chamber 220. Blood flow into housing interior 220 isprevented by the vent plug 900, which allows the pressurized air to flowthrough it, but seals, and sometimes completely seals, on contact withblood, thereby trapping the compressed air (at venous pressure) inhousing interior 220. Blood flow in the entire needle assembly ceasesonce the pressure within chamber 226 and the venous pressure are equal.

Once the steps set forth in the previous paragraph occur, and venousentry is visually confirmed by the phlebotomist, an evacuated container(not shown), is then inserted into the holder such that exterior end 260of second cannula 252 penetrates the stopper of the container, as knownin the art. Upon penetration of the stopper by second cannula 252, anegative pressure gradient is transmitted to chamber 226, causing bloodto flow from chamber 226 into the container.

The needle assemblies described above desirably should be small forconvenient use, but should be constructed to ensure reliable and rapidflashback. The occurrence of flashback in the needle assembliesdescribed and illustrated above operate pursuant to the ideal gas law.In particular, at very low densities all gases and vapors approach idealgas behavior and closely follow the Boyle's and Charles' laws given by:

P₁V₁=P₂V₂

where:

P₁ denotes the pressure of air within the needle assembly before needleinsertion;

P₂ denotes the pressure of air within the needle assembly after veinentry;

V₁ denotes the volume of air within the needle assembly before veinentry; and

V₂ denotes the volume of air within the needle assembly after veinentry.

Design parameters should keep the needle device as small as possible foreasy use, while ensuring an appropriate volume as specified by thepreceding equation. FIGS. 5 and 6 provide schematic representations ofthe needle assembly 210 of FIG. 1 for purposes of depicting theapplication of the ideal gas law. In this regard, A identifies thevolume of lumen 248 through inlet cannula 236. B denotes the totalvolume of the housing interior 220, flashback chamber 226, lumen 242through outlet cannula 252 and sealable sleeve 261. Referring again tothe preceding equation, P₁ is the pressure within needle assembly 210before use, and hence substantially equals atmospheric pressure.Atmospheric pressure will vary slightly from time to time and fromlocation to location. However, for purposes of this analysis,atmospheric pressure P₁ will be assumed to be 760 mm Hg. P₂ in thepreceding equation is the volume of the dead space in needle assembly210 after vein entry. More particularly, after vein entry, blood willfill lumen 248 of inlet cannula 236, thereby reducing the volume to beoccupied by gas in remaining portions of needle assembly 210 and henceincreasing the pressure of air in the remaining portion of needleassembly 210. A needle assembly with dimensions approximately as shownin FIG. 1 will have a pressure P₂ of about 790 mm Hg at venous pressure(with tourniquet). V₁ in the preceding equation defines the volume ofthe total dead spaced in needle assembly 210 before use, and hence willequal A+B as shown in FIG. 5. V₂ defines the dead space in the deviceafter vein entry, and with lumen 248 of inlet cannula 236 filled withblood. Hence, V₂ in the preceding equation will equal B. These inputparameters can be employed to define a minimum desired size for therespective components of needle assembly 200 as shown in the followingapplication of the ideal gas law equation.

P₁V₁=P₂V₂

P₁/P₂=V₂/V₁

760/790=B/(A+B)

0.962=B/(A+B)

0.962(A+B)=B

0.038B=0.962A

B=25.3A

Therefore, dead space in housing 212, outlet cannula 252 and sleeve 261advantageously is at least 25.3 times the volume defined by lumen 248through inlet cannula 236 and most advantageously is about 26 times thevolume of lumen 248. However, other configurations are possible and willfunction as described herein.

The immediate response when an evacuated tube is placed in communicationwith outlet cannula 252 is to draw blood from the vein into tube (notshown). The highest-pressure gradient is always maintained between thevein and the evacuated tube. An axially aligned inlet cannula 236 andoutlet cannula 252, therefore provide an unobstructed path for bloodflow from the vein into evacuated tube.

When the requisite tubes are filled with blood, the needle assembly isremoved from the vein. The sealed nature of the vent plug 900 inhibitsthe pressurized air within housing interior 220 from then moving intothe flashback chamber 226 and into the inlet cannula 236, which couldpromote dripping of blood from the IV cannula tip.

The preceding embodiments show structurally separate inlet and outletcannulas that are axially aligned with one other and placed in closeend-to-end relationship with one another. However, the principals of theinvention described above also can be achieved with a single cannulaformed with a transverse slot or aperture within the flashback chamber.For example, FIG. 7 schematically shows a needle assembly 310 with ahousing 312 and housing interior 320 that is substantially identical tohousing 212 described and illustrated above. Needle assembly 310 differsfrom needle assembly 210 in that a single double end needle cannula 336is provided and passes entirely through housing 312. More particularly,needle cannula 336 includes a venous entry end 338, a non-patient end340 and a lumen 342 extending therebetween. Portions of cannula 336within inner wall 324 include a slot or aperture 344 to providecommunication between lumen 342 and flashback chamber 326 within innerwall 324. Needle assembly 310 functions substantially in the same manneras needle assembly 210 described and illustrated above.

FIGS. 8-10, 11A, and 11B depict a needle assembly in yet a furtherembodiment of the invention. In certain embodiments of the needleassembly described with respect to FIGS. 1-7, the housing interiorincludes a vent plug 900, which seals the flashback chamber 226/326 fromthe housing interior 220/320. In such previously described embodiments,the vent plug is described as sealing upon flow of blood into theflashback chamber, thereby inhibiting any pressurized air that may buildup within the housing chamber 220/320 (such as upon displacement of airfrom the flashback chamber 226/326 into the housing chamber 220/320during the initial flash procedure) from moving in a reverse directiontoward the inlet cannula. In the embodiment of FIGS. 8-10, 11A and 11B,a porous vent is positioned within the housing at a location such thatthe vent divides the housing into two chambers having sizes anddimensions to establish predetermined volumes thereto. Moreover, theporous vent remains porous to blood and does not seal upon contact withblood. Desirably the blood does not contact the porous vent at theinitial flash indication, but such contact occurs at a later pointduring use of the assembly, as will be described in more detail herein.

For example, FIGS. 8-10, 11A, and 11B show a needle assembly 410 similarto that described in connection with FIG. 1-6 above. As shown in FIGS.8-10, 11A, and 11B, needle assembly 410 includes a housing 412 having afluid inlet end or first end 414 and a fluid outlet end or second end416. Needle assembly 410 includes exterior wall 418 defining the housinginterior. Exterior wall 418 extends generally longitudinally at thefirst end 414 forming an elongate longitudinal first portion 419 havinga first diameter. At second end 416, exterior wall 418 forms a secondportion 421 that has a second diameter that is generally larger than thefirst diameter of the first portion 419. Accordingly, housing 412 mayfoam a structure having a generally T-shaped cross-section. The exteriorwall 418 at second end 416 may be a separate element 428 that isattachable to main body portion 430 forming housing 412, therebyassisting in manufacture and assembly of needle assembly 410. Firstportion 419 and second portion 421 may be arranged relative to eachother in a variety of arrangements, so long as they are capable offunctioning for transport of air therebetween as discussed herein.

Needle assembly 410 further includes a fluid inlet cannula 436 extendingfrom first end 414 of housing 412. Fluid inlet cannula 436 includes anexterior end that defines a first puncture tip such as a sharpened bevelat patient puncture tip 438, and extends within first end 414 of housing412 at open end 429, and may be fixedly mounted therein. Fluid inletcannula 436 is characterized further by a substantially cylindricallumen extending between the ends and communicating with the interior ofhousing 412.

Needle assembly 410 also includes a second puncture tip such asnon-patient puncture tip 462 extending from second end 416 of housing412. As seen in FIG. 10, this may be accomplished by providing needleassembly 410 with a second cannula in the form of fluid outlet cannula452. In particular, the end of fluid outlet cannula 452 may define asharpened bevel forming non-patient puncture tip 462. Fluid outletcannula 452 extends within second end 416 of housing 412, and may befixedly mounted therein. Fluid outlet cannula 452 is characterizedfurther by a substantially cylindrical lumen communicating with theinterior of housing 412. Outlet cannula 452 is mounted within housing412 so that an interior end 464 passes substantially coaxially thereinsuch that outlet cannula 452 substantially aligns axially with theinterior end of inlet cannula 436. Desirably, this is achieved bymounting outlet cannula 452 at a location adjacent second end 416 ofhousing 412, such that the interior end 464 of outlet cannula 452extends within housing 412 to a location adjacent the interior end 439of inlet cannula 436. As seen in FIG. 11B, the interior end 464 ofoutlet cannula 452 is spaced only a small distance from the interior end439 of inlet cannula 436, thereby forming an axial gap therebetween forflow of blood into flashback chamber 426 about outlet cannula 452. Thedistance between the interior end 464 of outlet cannula 452 and theinterior end 439 of inlet cannula 436 foaming the axial gap issufficient to provide for flow of blood into flashback chamber 426,based upon the patient's blood pressure after venipuncture. In certainembodiments, an axial gap that is less than 0.5 mm may result in aflashback that is inconsistent.

As seen in FIG. 11B, fluid inlet cannula 436 and fluid outlet cannula452 are positioned and dimensioned within housing 412 so as to achieveboth desirable flow of blood through assembly 410 and to achieveeffective flashback indication. In particular, wall 418 of housing 412is dimensioned to provide a radial gap around outlet cannula 452 ofabout 0.2 mm at an area surrounding the internal end 464 thereof. Thisgap achieves a substantially laminar blood flow within flashback chamber426 and prevents blood hemolysis. Additionally, the small radial gapbetween the inner surface of wall 418 and outlet cannula 452 at the areasurrounding the internal end 464 enables a drop of blood to be spreadthinly across the radial gap in flashback chamber 426 to provide amagnified flashback indication with a very small volume of blood. Thus,an easily visualized flashback indication is achieved quickly at thefirst appearance of blood within flashback chamber 426. It iscontemplated that internal end 464 of outlet cannula 452 may bepartially supported within housing 412, so long as blood flow intoflashback chamber 426 is achieved about the internal end 464.

In an alternate arrangement, a single cannula is provided, similar tothat embodiment discussed in connection with FIG. 7. Such an arrangementis depicted in the embodiment of FIG. 12A and 12B (shown in connectionwith a blood collection assembly as will be described in more detailherein). In such an arrangement, the fluid inlet cannula and the fluidoutlet cannula represent one single cannula 470, having a patientpuncture tip 438 a non-patient puncture tip 462, and a lumen 442extending therethrough, and with the body of the cannula 470 beingfixedly attached to a portion of the housing 412 and passing entirelythrough housing 412. A portion of cannula 470 extending through housing412 includes one or more openings such as a slot or aperture 444 toprovide communication between lumen 442 and flashback chamber 436 withinhousing 412. In the embodiment seen in FIGS. 12A and 12B, twosemi-circular cuts forming the aperture are shown on opposing sides ofcannula 470, although it is contemplated that any number of suchopenings can be included to provide for blood flow into flashbackchamber 426.

Returning to the embodiment of FIGS. 8-10, 11A, and 11B, needle assembly410 further includes a sealable sleeve 461 mounted to fluid outlet end416 of housing 412. This may be accomplished by providing a mountingprotrusion 429 at second end 416 of housing 412, such as on element 428,with sealable sleeve 461 representing an elastomeric element that can befrictionally fit or otherwise affixed over protrusion 429. Sealablesleeve 461 covers non-patient puncture tip 462 at the exterior end ofoutlet cannula 452 when sealable sleeve 461 is in an unbiased condition.However, sealable sleeve 461 can be collapsed in response to pressureexerted by the stopper of an evacuated tube for urging exterior end 462of outlet cannula 452 through both sealable sleeve 461 and the stopperof an evacuated tube, as known in the art.

The embodiment of FIGS. 8-10, 11A, and 11B further includes a porousvent 910 positioned within the interior of housing 412. Porous vent 910is positioned within housing 412 to divide housing 412 into two distinctchambers, namely, a first chamber represented by flashback chamber 426and a second chamber represented by secondary chamber 427. Porous vent910 may be constructed of a suitable material as described above withrespect to vent plug 900, albeit without the hydrophilic material thatswells on contact. In this manner, porous vent 910 is adapted to ventair therethough, and represents a porous structure including a pluralityof pores that allow for passage of blood therethrough without sealingfrom fluid flow therethrough upon contact with blood, as is known in theart with vent plugs including a hydrophilic material. As discussed inmore detail herein, during use of needle assembly 410, the internalpores within porous vent 910 at least partially fill with blood due tothe negative pressure established within secondary chamber 427. Suchfilled pores in combination with the negative pressure within secondarychamber 427 prevent air flow between the secondary chamber 427 and theflashback chamber 426, and provide for fluid resistance of the bloodflow through porous vent 910, as will be described in further detail.

Desirably, porous vent 910 is positioned within the interior of housing412 between first portion 419 and second portion 421. In this manner,first portion 419 of housing 412 essentially defines the flashbackchamber 426, and second portion 421 of housing 412 essentially definesthe secondary chamber 427. Alternatively, porous vent 910 may bepositioned within the interior of housing 412 at a location spanning thetransition between the first diameter of first portion 419 and thesecond diameter of second portion 421, as shown in the embodiment ofFIGS. 12A and 12B. In any event, porous vent 910 is generally acylindrically-shaped member with a central opening therein axiallyencircling a portion of the cannula, particularly fluid outlet cannula452.

The interior volume of housing 412 is defined by the sum of the volumesof flashback chamber 426 and secondary chamber 427 as well as the volumerepresented by the pores of porous vent 910. Such interior volume isconfigured so as to provide for certain attributes to the needleassembly 410, in particular with respect to the ability of the secondarychamber 427 to be at least partially evacuated of a portion of the airtherein to establish a negative pressure therein upon application of anevacuated tube to needle assembly 410 during use thereof Such negativepressure within secondary chamber 427 draws blood through the pores ofporous vent 910 based on when blood contacts porous vent 910 andpartially fills the pores thereof In a particular embodiment of theinvention, the overall interior volume of housing 412 may be from about300 mm³ to about 400 mm³. Such a volume is particularly useful for theintended use of needle assembly 410 for conventional venipuncture fordrawing a blood sample from a patient using a needle cannula having aconventional gauge for venipuncture as is known in the art. Such avolume also enables the needle assembly to be particularly useful withpatients having relatively low blood pressure, in that the interiorvolume of the housing 412 is sufficient so as to allow adequatedisplacement of air so that blood will travel the complete length offluid inlet cannula 436 and into flashback chamber 426.

Porous vent 910 is desirably positioned within housing interior so as todefine flashback chamber 426 as having a volume that represents fromabout 5 percent to about 20 percent of the total overall volume ofhousing 412, desirably from about 7 percent to about 12 percent of thetotal overall volume of housing 412, including the volume of secondarychamber 427 and the volume of the pores within porous vent 910. In thismanner, the remaining internal volume of housing 412, defined by theinternal volume positioned downstream from the interface between porousvent 910 and flashback chamber 426 including the internal pores ofporous vent 910 and the volume of secondary chamber 427, represents asignificant portion of the internal volume of housing 412. Such a ratioof the flashback chamber 426 to the total overall volume of the housing412 assures that flashback chamber 426 has sufficient volume to properlyvisualize the initial flash, desirably while preventing blood from fullycontacting the porous vent 910 at initial venipuncture, based on theinitial build-up of pressure within secondary chamber 427 caused byvenous pressure forcing the blood into flashback chamber 426. Suchvolume ratios are effective for the intended use as described in furtherdetail herein, wherein blood flowing into flashback chamber 426 uponinitial venipuncture does not fully contact porous vent 910, anddesirably does not contact porous vent 910, and wherein at least aportion of the air is drawn out from secondary chamber 427 based uponapplication of an evacuated blood collection tube to the needle assembly410. In this manner, secondary chamber 427 can effectively draw bloodfrom within flashback chamber 426 and from within fluid inlet cannula426 toward secondary chamber 427, such as into and through the pores ofporous vent 910, so that when the patient puncture tip 438 is removedfrom the patient and is exposed to the external environment, blood isdrawn away from the pucture tip 438, preventing the leakage of blooddroplets from the puncture tip 438. In one particular embodiment, thetotal interior volume of the housing 412 is about 380 mm³, with theflashback chamber 426 having a volume of about 30 mm³, the secondarychamber 427 having a volume of about 300 mm³, and the pores of theporous vent 910 representing a volume of about 50 mm³.

Needle assembly 410 may be assembled as follows. Fluid inlet cannula 436is positioned through first end 414 of housing 412 such that the openinterior end 439 is positioned within an interior portion of housing 412at first portion 419 and patient puncture tip 438 extends externally offirst end 414. Fluid outlet cannula 452 is positioned within housing 412through the opposite end, such that open internal end 464 is positionedwithin an interior portion of housing 412 at first portion 419 adjacentinterior end 439 of fluid inlet cannula 436, with a slight gaptherebetween, and with non-patient puncture tip extending externally ofsecond end 416. Fluid inlet cannula 436 and fluid outlet cannula 452 maybe affixed therein in any known manner, desirably through a medicalgrade adhesive.

In alternate embodiments including only a single cannula 470, suchcannula 470 is affixed within housing 412 such that opening 444 ispositioned within the interior of housing 412 at first portion 419, withpatient puncture tip 438 extending externally of first end 414 andnon-patient puncture tip 462 extending externally of second end 416.

Porous vent 910 is then inserted within housing 412 and positioned overfluid outlet cannula 454 (or over the single cannula 470), and element428 is thereafter affixed to the second end 416, enclosing the interiorof housing 412. Sealable sleeve 461 is then affixed over protrusion 429.As such, the interior of housing 412 is closed from the externalenvironment, with the sole path for fluid communication between theinterior of housing 412 and the external environment being providedthrough the patient puncture tip 438.

Needle assembly 410 assembled as such can be used in connection with ablood collection tube holder 800, as depicted in the embodiment shown inFIGS. 12A and 12B. Such assembly may be accomplished through the rearopen end of blood collection tube holder 800, so that the entire needleassembly 410 is inserted to a portion where at least patient puncturetip 438 and at least a portion of inlet cannula 436 extend out throughthe front end of blood collection tube holder 800. In embodiments wheresecond portion 421 of needle assembly 410 is radially larger than firstportion 419, such an insertion and arrangement enables the secondarychamber 427 to be fully contained within the internal space withincollection tube holder 800, and with flashback chamber 426 extending outfrom a front end thereof

In use, needle assembly 410 may be provided with collection tube holder800 attached thereto. Patient puncture tip 438 is inserted through theskin of a patient and into the patient's vasculature, desirably into avein. Upon venipucture, a closed environment is achieved within housing412, since housing 412 is an entirely closed structure, and sincesealable sleeve 461 closes off the only outlet of housing 412 (i.e.,fluid outlet cannula 452). The patient's blood pressure causes blood toflow through patient puncture tip 438, into fluid inlet cannula 436, andout interior end 439 (or through opening 444 in the embodiment of FIGS.12A and 12B), into flashback chamber 426 surrounding interior end 464 ofoutlet cannula 452. The transparent or translucent nature of housing 412permits visualization of the blood within flashback chamber 426,providing an indication that venipuncture is achieved.

Since the interior of housing 412 is a closed environment, the flow ofblood into flashback chamber 426 causes air to be trapped within thehousing interior, including within flashback chamber 426, porous vent910 and secondary chamber 427, as well as within fluid outlet cannula452, causing such trapped air to be slightly pressurized therein.Flashback chamber 426 and secondary chamber 427 are configured throughtheir size and dimensions such that the volumes thereof permit blood toflow into flashback chamber 426 at this initial venipucture, but thebuild up of air pressure within the pores of porous vent 910 and withinsecondary chamber 427 prevents blood from fully contacting porous vent910, and desirably prevents blood from even partially contacting porousvent 910 at the initial venipuncture.

After such initial venipuncture and flash visualization, a samplecollection container having a negative pressure therein, such as anevacuated blood collection tube (not shown) as is commonly known in theart, is inserted within the tube holder 800. The stopper (not shown) ofsuch evacuated container contacts and displaces sealable sleeve 461,causing non-patient puncture tip 462 to puncture through sealable sleeve461 and through the stopper of the evacuated container. At this point,fluid communication is established between the non-patient puncture tip462 and the interior of the evacuated collection container. The negativepressure within the evacuated collection container draws the blood thathas collected within flashback chamber 426 into fluid outlet cannula 452and into the evacuated collection container. Along with the blood withinflashback chamber 426, the negative pressure within the evacuatedcollection container will also draw at least a portion of the air out ofthe flashback chamber 426 and out of the secondary chamber 427 throughthe pores of porous vent 910, toward and into the evacuated collectioncontainer. In addition, the close proximity and alignment of fluidoutlet cannula 452 and fluid inlet cannula 436 causes blood to be drawnfrom fluid inlet cannula 436 and from the patient, simultaneously withsuch air being drawn from the flashback chamber 426 and secondarychamber 427.

Such drawing of air reduces the pressure within the flashback chamber426 and the secondary chamber 427, establishing a negative pressuretherein with respect to the patient's bloodstream and with respect tothe external environment. This negative pressure that has beenestablished within the interior of housing 412, and specifically withinflashback chamber 426 and secondary chamber 427, draws additional bloodfrom within fluid inlet cannula 436 and from the patient into flashbackchamber 426, with the blood contacting porous vent 910. With such bloodfilling flashback chamber 426, the blood fully contacts the surface ofporous vent 910 that extends within flashback chamber 426, and begins tofill the pores of porous vent 910. Such filling of the pores of porousvent 910 that are directly at the interface of porous vent 910 andflashback chamber 426 closes off the porous vent from airflowtherethrough, but does not fully act as a seal, in that the blood doesnot cause the material of the porous vent to swell or close off to airflow, but instead merely physically fills the voids within the porousvent. Moreover, since a portion of the air within secondary chamber 427has been drawn out from secondary chamber 427, secondary chamber 427represents a closed chamber with a negative pressure therein relative tothe external environment. Since the volume of secondary chamber 427represents a substantial portion of the overall interior volume ofhousing 412, a significant portion of interior volume of housing 412downstream of the filled pores at the interface of porous vent 910 andflashback chamber 426 remains at a negative pressure with respect to theremainder of the interior volume. Secondary chamber 427 will thereforecontinue to have a drawing effect on the blood within the pores ofporous vent 910 and within flashback chamber 426 through the pores ofporous vent 910 toward secondary chamber 427, without releasing any airfrom the secondary chamber 427 in the opposite direction due to thepores of porous vent 910 at the interface of the flashback chamber 426being filled with blood, thereby effectively preventing air flow throughporous vent 910 due to the filled pores. The draw created by thenegative pressure within secondary chamber 427 has a fluid resistancebased on the blood filling the pores of porous vent 910 and based on thetortuous path created by the pores of porous vent 910, and therefore isa gradual draw with reduced fluid movement.

At this point, the evacuated collection container and the secondarychamber 427 are both at a negative pressure with respect to the externalenvironment (and with respect to the patient's bloodstream), andtherefore both effect a draw from the fluid inlet cannula 436. Thismutual drawing effect may essentially establish an equilibrium withinthe flashback chamber 426, such that the blood contained within theflashback chamber 426 is not drawn toward or into either the secondarychamber 427 through the pores of porous vent 910 or into the evacuatedcollection container through the fluid inlet cannula 436, but insteadessentially remains within flashback chamber 426 in a steady state. Thenegative pressure of the evacuated collection container draws blooddirectly from the patient through fluid inlet cannula 436, due to theclose proximity and alignment of fluid outlet cannula 452 and fluidinlet cannula 436, as well as due to the equilibrium established withinflashback chamber 426 (based on the opposite draw forces between theevacuated collection container and the evacuated secondary chamber 427).The continual draw of blood into the evacuated collection containergradually causes the pressure within the collection container toincrease.

Once the evacuated collection container is filled with the desiredamount of blood, the container is removed from the non-patient puncturetip 462, thereby releasing the fluid communication between thenon-patient puncture tip 462 and the evacuated collection container,with sealable sleeve 461 then covering and closing off non-patientpuncture tip 462. Absent such draw from the negative pressure of theevacuated collection tube, the negative pressure within the secondarychamber 427 effects a slight draw on the blood within flashback chamber426 through the pores of porous vent 910. Such draw, however, is slowand gradual, due to the tortuous path of blood flow through the pores ofporous vent 910.

Additional evacuated collection containers can thereafter be insertedinto tube holder 800 and used for sample collection through non-patientpuncture tip 462 as described above, by placing a second evacuatedcollection container within the holder 800 and establishing fluidcommunication between the non-patient puncture tip 462 and the interiorof the evacuated collection container by puncturing the stopper, asdiscussed. In such further sampling, the evacuated collection containerand the secondary chamber 427 are both at a negative pressure, andtherefore both effect a draw from the fluid inlet cannula. As above,this effect essentially establishes an equilibrium within the flashbackchamber 426, thereby preventing the blood contained within the flashbackchamber 426 from being drawn toward or into either the secondary chamber427 (through the porous vent 910). The negative pressure of theevacuated collection container draws blood directly from the patientthrough fluid inlet cannula 436 as discussed above, due to the closeproximity and alignment of fluid outlet cannula 452 and fluid inletcannula 436. Once any such additional evacuated collection containersare filled with the desired amount of blood, the container is removedfrom the non-patient puncture tip 462, thereby releasing the fluidcommunication between the non-patient puncture tip 462 and the evacuatedcollection container, with sealable sleeve 461 then covering and closingoff non-patient puncture tip 462.

Once all of the desired blood samples have been drawn in this manner,patient puncture tip 438 is removed from the vasculature of the patient(i.e., from the bloodstream), thereby exposing the opening of patientpuncture tip 438 to the external environment. Since the solecommunication path between the housing interior and the externalenvironment is through patient puncture tip 438, the negative pressureestablished within secondary chamber 427 relative to the externalenvironment will affect a gradual draw on the blood contained withinflashback chamber 426 and within fluid inlet cannula 436 toward andthrough porous vent 910. Such drawing effect will displace and move anyblood contained within fluid inlet cannula 436 away from patientpuncture tip 438, toward secondary chamber 427, thereby preventing anyblood from leaking from patient puncture tip 438 out of fluid inletcannula 436. Such negative pressure within secondary chamber 427 maycontinue to have a gradual drawing effect through the porous vent 910for a prolonged period of time after removal of patient puncture tip 438from the patient, and may draw all of the remaining blood containedwithin fluid inlet cannula 436 and flashback chamber 426 through porousvent 910 and/or into secondary chamber 427. Needle assembly 410 can thenbe properly disposed of in known manner.

FIGS. 13A, 13B, and 13C depict yet a further embodiment of a needleassembly. The needle assembly shown in FIGS. 13A-13C is similar to theembodiment described above in connection with FIGS. 8-10, 11A, and 11B,albeit with the secondary chamber further comprising a plurality ofinterior regions that are in fluid communication with each other, anddesirably gas venting fluid communication, to define the interior volumeof the secondary chamber.

In particular, as depicted in FIG. 13A, needle assembly 510 includes ahousing 512 having a fluid inlet end or first end 514 and a fluid outletend or second end 516. Needle assembly 510 further includes a fluidinlet cannula 536 extending from first end 514 of housing 512. Fluidinlet cannula 536 extends between an exterior end that defines a firstpuncture tip such as a sharpened bevel at patient puncture tip 538, andan interior open end 539 extending within first end 514 of housing 512,and may be fixedly mounted therein. Fluid inlet cannula 536 ischaracterized further by a substantially cylindrical lumen extendingbetween the ends and communicating with the interior of housing 512.

Needle assembly 510 also includes a second puncture tip such asnon-patient puncture tip extending from second end 516 of housing 512,such as through a second cannula in the form of fluid outlet cannula552. In particular, the end of fluid outlet cannula 552 may define asharpened bevel forming non-patient puncture tip 562. Fluid outletcannula 552 extends within second end 516 of housing 512, and may befixedly mounted therein. Fluid outlet cannula 552 is characterizedfurther by a substantially cylindrical lumen communicating with theinterior of housing 512. Outlet cannula 552 is mounted within housing512 so that an interior end 564 passes substantially coaxially thereinsuch that outlet cannula 552 substantially aligns axially with theinterior end of inlet cannula 536, in a similar manner as discussed inconnection with the embodiment depicted in FIGS. 8-10, 11A, and 11Bdescribed above. For example, the interior end 564 of outlet cannula 552may be spaced only a small distance from the interior end 539 of inletcannula 536, thereby forming an axial gap therebetween for flow of bloodinto flashback chamber 526 about outlet cannula 552 as shown in FIG.13C, or may be a single cannula having an opening therein, as describedin connection with the embodiment of FIGS. 12A-12B.

As shown in FIGS. 13A-13C, needle assembly 510 includes a generallyelongate longitudinal portion at first end 514, which generally includesan interior wall 515 and an exterior wall 517. Interior wall 515 extendsgenerally longitudinally within housing 512, with a first diameterdefining an interior chamber in the form of flashback chamber 526.Second end 516 defines a second portion having a second diameter that isgenerally larger than the first diameter of interior wall 515. Interiorwall 515 is dimensioned to provide a radial gap around outlet cannula552 of about 0.2 mm at an area surrounding the internal end 564 thereof,thereby achieving a substantially laminar blood flow within flashbackchamber 526, as discussed above. Internal end 564 of outlet cannula 552may be supported within housing 512, as in the embodiment discussedabove. Needle assembly 510 may further include a sealable sleeve 561mounted to fluid outlet end 516 of housing 512, such as through amounting protrusion 529, as discussed above.

As with the embodiment of FIGS. 8-10, 11A, and 11B, needle assembly 510further includes a porous vent 910 a positioned within the interior ofhousing 512. Porous vent 910 a is generally a cylindrically-shapedmember with a central opening therein axially spaced from and encirclinga portion of the cannula, particularly fluid outlet cannula 552. Porousvent 910 a may be constructed of any suitable material as describedabove in connection with the embodiment of FIGS. 8-10, 11A, and 11B.Porous vent 910 a is positioned within housing 512 in a manner such thathousing 512 is divided into at least two distinct chambers, namely, afirst chamber represented by flashback chamber 526 and a second chamber,representing the total internal volume of housing 512 that is positioneddownstream of porous vent 910 a. The term downstream is used herein torepresent location with respect to the intended flow of blood throughthe housing 512 of needle assembly 510, i.e., blood flows throughhousing 512 from patient puncture tip 538 at fluid inlet cannula 536,through open end 539, into flashback chamber 526, into porous vent 910a, and toward the secondary chamber.

Porous vent 910 a may be positioned within the interior of housing 512at a location spanning the transition between the first end 514 and thesecond end 516. The interior volume of housing 512 is defined by the sumof the volumes of the flashback chamber and the secondary chamber aswell as the volume represented by the pores of porous vent 910 a. Suchinterior volume is configured so as to provide for certain attributes tothe needle assembly 510, in particular with respect to the ability ofthe secondary chamber to be at least partially evacuated of a portion ofthe air therein to establish a negative pressure therein uponapplication of an evacuated tube to needle assembly 510 during usethereof, as described in connection with the embodiments set forthabove. Such negative pressure within the secondary chamber draws bloodinto the pores of porous vent 910 a based on when blood contacts porousvent 910 a at the interface between the porous vent 910 a and flashbackchamber 526 and partially fills the pores thereof

In the embodiment of FIGS. 13A-13C, the secondary chamber comprises aplurality of distinct interior regions, such as a first interior region527 a and a second interior region 527 b. In particular, in theembodiment of FIGS. 8-10, 11A, and 11B, the secondary chamber 427represents a radially enlarged portion at the second end 416 of housing412, which enlarged portion accommodates the proper size of porous vent910 and the proper internal volume required for secondary chamber 427 tofunction in the intended manner (i.e., to represent a substantial volumeof the total interior volume of housing 512 so as to be able toestablish a negative pressure therein during use, as described above).When used in connection with traditional blood collection needleassemblies, it is desirable to maintain a low profile for the assembly.This may be accomplished by providing for a reduced overall profile, andin particular an overall reduced diameter, of the secondary chamber.

In order to maintain the appropriate volume of the secondary chamber forthe intended use, the secondary chamber may extend longitudinally alongthe housing 510. It is important, however, to ensure that sufficientvolume exists between the secondary chamber and the pores of porous vent910 a in order to ensure a sufficient drawing effect once the secondarychamber is evacuated in its intended use. Accordingly, the secondarychamber may be divided into a plurality of regions, such as in theembodiment of FIGS. 13A-13C, in which the secondary chamber includesfirst interior region 527 a and second interior region 527 b, with firstand second interior regions 527 a, 527 b in fluid communication witheach other through porous vent 910 a, and also in fluid communicationwith respect to flashback chamber 526 downstream of flashback chamber526. In this manner, the total volume of the secondary chamberdownstream of the flashback chamber, which is made up of a plurality ofinterior regions separated by the porous vent, is sufficient to achievethe intended use of the device as described herein, by maintaining thesecondary chamber as a significant amount of the total volume of theneedle housing.

While the present embodiment depicts two interior regions 527 a and 527b, it is contemplated that the number of interior regions can be anynumber, so long as the total interior volume of the secondary chamber(represented by the total volume of the combined interior regionspositioned downstream of porous vent 910 a), define a downstreamsecondary chamber volume corresponding to the volume and ratiosdescribed above with respect to the embodiment of FIGS. 8-10,11A, and11B.

First interior region 527 a of the secondary chamber may generally belocated adjacent the second end 516 of housing 512, while secondinterior region 527 b of the secondary chamber may be positionedgenerally concentric about a portion of the flashback chamber 526. Thismay be accomplished by providing housing 512 as a two-part housing, withfirst end 514 representing a main body portion 530 of the housing, andsecond end 516 representing a separate body portion 528 of the housingthat is attachable to the main body portion 530, forming housing 512.For example, main body portion 530 of the housing may include interiorwall 515 defining flashback chamber 526 and exterior wall 517 definingsecond interior region 527 b. Main body portion 530 extends generallyalong the axis defining needle assembly 510 to define an elongatelongitudinal portion, with interior wall 515 defining a first diameterfor flashback chamber 526, and exterior wall 517 defining a seconddiameter for second interior region 527 b. The exterior wall of separatebody portion 528 at second end 516 of housing 512 generally defines thefirst interior region 527 a, and exterior wall 517 of main body portion530 of housing 512 generally defines second interior region 527 b. Inthis manner, second interior region 527 b extends distally from theporous vent 910 a longitudinally and annularly surrounding a portion offlashback chamber 526. Desirably, both interior wall 515 and exteriorwall 517 are transparent or translucent, such that the contents offlashback chamber 526 (such as blood flow therein) can be viewablethrough the second interior region 527 b and/or through the firstinterior region 527 a.

Exterior wall 517 of housing 512 may generally taper from a largerdiameter to a smaller diameter toward first end 514. A portion ofexterior wall 517 shown in FIG. 13B at portion 517 p may include asubstantially constant diameter for accommodating porous vent 910 atherein in a tightly sealed arrangement. Alternatively, porous vent 910a may include dimensions that taper to coincide with the interior wallsurface along tapering exterior wall 517.

FIGS. 14-16 depict a further embodiment, in which needle assembly 510 isshown in use in connection with a safety blood collection needleassembly, including tube holder 810 for accommodating an evacuated bloodcollection tube (not shown) during a standard blood collection procedurein known manner, and a pivoting safety shield 812 for protecting theneedle after use of the blood collection needle assembly.

In use, needle assembly 510 works in substantially the same manner asneedle assembly 410 described above in connection with FIGS. 8-10, 11A,11B, 12A, and 12B, with first and second interior regions 527 a, 527 bacting in the same manner as secondary chamber 427 described in theprior embodiment. In particular, needle assembly 510 is provided incombination with a tube holder, such as tube holder 810. Uponvenipuncture of fluid inlet cannula 536 with a patient, blood flows intofluid inlet cannula 536 based on blood pressure of the patient and outthe open end 539 thereof, into flashback chamber 526, such as shown inFIG. 13A, for visualization of blood flow, but does not fully contactthe pores of porous vent 910 a. After flash visualization, an evacuatedblood collection container is inserted into tube holder 810 for piercingby the non-patient puncture tip 562 of fluid outlet cannula 552, whichdraws blood out from flashback chamber 526 and draws air out from firstand second interior regions 527 a, 527 b, thereby reducing the pressurewithin flashback chamber 526 and first and second interior regions 527a, 527 b, in a manner as described above. Thereafter, the negativepressure within flashback chamber 526 and first and second interiorregions 527 a, 527 b draws blood from the patient through fluid inletcannula 536, fully contacting the surface of porous vent 910 a at theinterface between porous vent 910 a and flashback chamber 526 to fillthe pores thereof. Since the interior volume within first and secondinterior regions 527 a, 527 b has been evacuated, first and secondinterior regions 527 a, 527 b represent a closed environment with anegative pressure therein, and therefore continue to have a drawingeffect on the blood within the filled pores of porous vent 910 a andwithin flashback chamber 526, as discussed above. Once all tubes arefilled and removed, the negative pressure is maintained within first andsecond interior regions 527 a, 527 b due to the filled pores of porousvent 910 a sealing off first and second interior regions 527 a, 527 bfrom the external environment, and such negative pressure within firstand second interior regions 527 a, 527 b continues to affect a gradualdraw on the blood contained within the pores of porous vent 910 a andflashback chamber 526 and within fluid inlet cannula 536 away frompatient puncture tip 538, thereby preventing any blood from leaking frompatient puncture tip 538. Such continual draw may cause blood to flowcompletely through the pores of porous vent 910 a and into one or bothof first and second interior regions 527 a, 527 b.

Reference is now made to FIGS. 17 and 21 which show a cross-sectionalview of the needle assembly of the invention according to anotherdesign, generally indicated as 610, and having a porous vent 920including a blocking member 925 located within the porous vent 920.According to this needle design, the needle assembly 610 includes ahousing 612 defining a housing interior 620. The housing includes afirst fluid inlet end 614, a second fluid outlet end 616, and anexterior wall 618 extending between the ends 614 and 616. The housing612 includes a cylindrical interior wall 624 that extends in the housinginterior 620. The exterior wall 618 includes a frusto-conical shapedportion 618 a that extends toward the first fluid inlet end 614. Thisfrusto-conical shaped portion 618 a, the porous vent 920, and thecylindrical interior wall 624 define a flashback chamber or firstchamber 626. The cylindrical interior wall 624, the exterior wall 618 ofthe housing, and a portion of the second fluid outlet end 616 define asecond chamber 627. The first chamber 626 and the second chamber 627 areseparated by a central aperture opening 628. The housing comprises atleast one cannula 632 a, 632 b, as shown in FIG. 21 having a patientpuncture tip 638 extending from a first end 614 of the housing 612 and anon-patient puncture tip 662 extending from a second end 616 of thehousing 612. The non-patient puncture tip 662 and the patient puncturetip 638 are in fluid communication with each other within the housinginterior 620.

Needle assembly 610 may be assembled according to one design as follows.Fluid inlet cannula 632 is positioned through first end 614 of housing612 such that the open interior end 639 is positioned within an interiorportion of housing 612 and patient puncture tip 638 extends externallyof first end 614. Fluid outlet cannula 652 is positioned within housing612 through the opposite end, such that open internal end 664 ispositioned within an interior portion of housing 612 adjacent interiorend 639 of fluid inlet cannula 632, with a slight gap therebetween, andwith non-patient puncture tip extending externally of second end 616.Fluid inlet cannula 632 and fluid outlet cannula 652 may be affixedtherein in any known manner, desirably through a medical grade adhesive.

This type of needle design assembly is also shown in FIGS. 13A-13C whichshows a first fluid inlet cannula 536 extending from the housing 512,comprising the patient puncture tip 538 and a second fluid outletcannula 552 extending from the housing 512, comprising the non-patientpuncture tip 562. The first cannula 536 and the second cannula 552 aresubstantially axially aligned within the housing interior 520 andseparated from each other by a gap between an interior end 539 of thefirst inlet cannula 536 and an interior end 564 of the second outletcannula 552, the gap being in fluid communication with the first chamber526 of the housing.

It can be appreciated that the alternative design, as discussed inrelation to FIGS. 12A-12B can be used for the needle assembly shown inFIGS. 17 and 21 wherein only a single cannula is affixed within housing612, such that an opening is positioned within the interior of housing612, with patient puncture tip 638 extending externally of first end 614and non-patient puncture tip 662 extending externally of second end 616.

The porous vent 920 is positioned within the housing interior 620 toseparate the housing interior 620 into the first chamber 626 and thesecond chamber 627. The porous vent 920 includes pores for passage offluid therethrough from the first chamber 626 to the second chamber 627and the sole communication path between the housing interior 620 and theexternal environment is via the patient puncture tip 638.

The porous vent 920 of the present invention is configured to controlflow of the fluid such that the fluid flows in an axial directiontherethrough, as specifically shown in FIG. 21. The porous vent 920, asshown in FIGS. 18-19, comprises a tubular member having a first end face930, a second end face 932, and a central portion 934 extending betweenthe first end face 930 and the second end face 932. The tubular memberincludes an axial hole 936 configured for surrounding at least a portion632 b of the at least one cannula 632 a, 632 b and the blocking member925 causes the fluid (air and blood) to flow along a controlledlongitudinal path from the first end face 930 to the central portion 934along a length L, as shown in FIG. 21, and/or to the second end face 932of the porous vent 920 and, according to the design shown in FIGS. 17and 21, through the central aperture opening 628 between the firstchamber 626 and the second chamber 627 wherein the central apertureopening 628 is located adjacent to the central portion 934 of the porousvent 920.

As illustrated in FIG. 20, when using a porous vent 920 a′ without theblocking member 925 of the present invention, the fluid (air and blood)would enter into the porous vent 920 a′ through either or both of thefirst end face 930 a′ and/or a second end face 932 a′ of the porous vent920 a′ and through the surface of the plug hole and flow outward throughthe porous media toward the second chamber 627 a′ along a plurality ofradial paths in a random manner along the path of least resistance andsubsequently through central aperture opening 628 a′ separating thefirst chamber 626 a′ from the second chamber 627 a′. Alternatively, thefluid would flow at the seal interface with the plastic hub housings 612a′. The low resistance of the porous vent media 920 a′ can result inpooling of blood in the second chamber 627 a′ which depletes thedifferential pressure between the housing interior 620 a′ and theatmosphere. Consequently, this depleted differential pressure can resultin a blood droplet being expelled from the patient puncture tip (notshown) when an evacuated tube is removed from the non-patient puncturetip (not shown) and the needle cannula 632 a′ is removed from thepatient and exposed to atmospheric pressure due to the higher pressurebeing present in the hub.

The addition of the blocking member 925 to the inside diameter and/oralong the axial bore 936 of the porous vent 920, according to thepresent invention and shown in FIGS. 18 and 19, prevents fluid fromflowing radially along the shortest path from the inside diameter to theoutside diameter of the porous vent 920. In particular, the presentinvention causes the fluid (blood and air) to flow axially or along thelongest path through the porous vent 920, as shown in FIG. 21, through acontrolled length of the porous media of the vent 920 from the end faces930, 932 toward the central aperture opening 628 into the second chamber627. The added blocking member 925 creates a longer and more tortuouspath through the media which improves the fluid resistance and helps toretain differential vacuum in the second chamber 627.

Referring back to FIGS. 17-19, the blocking member 925 can comprise abushing press-fitted into the inside surface 938 of the porous vent 920.According to one design, the bushing can be a stainless steel cannulacut to the length of the porous vent 920. One example can include a cut17 gauge 302 stainless steel cannula press-fit as a bushing into theinternal diameter of a sintered polyethylene cylindrical porous venthaving a 7-12 micron pore size range. This particular arrangement hasbeen found to have a slower decay of vacuum within the second chambereven after multiple tube draws, reduced pooling of blood into the secondchamber, reduced bubbling in the flash chamber, and reduced blooddroplet occurrences. Other examples of bushings include extruded plastictubing and tubular molded parts. Other blocking members for 925 caninclude potting an annular space between the porous vent 920 and the atleast one cannula 632 with an adhesive or sealant or blocking an endface 930, 932 of the porous vent 920 or any other location of the porousvent 920 to limit the flow path of fluid from the first chamber 626 tothe second chamber 627 and maximize the tortuous flow length and ventresistance. According to yet another design, the blocking member 925 canbe formed by melting or fusing a portion of the porous vent 920 on theinside surface portion 938 to render this portion non-porous. Themelting or fusing of the vent 920 can be achieved by either heat orultrasonic friction to the inside diameter portion 938 of the vent 920.According to still another design, the blocking member 925 can be aseparate member, such as a plastic tubular member, that is placed inabutting relationship with respect to the inside surface 938 of theporous vent 920.

Referring back to FIGS. 12A-12B and previously discussed in relation toFIG. 21, the first and second cannulas 632, 652 can be replaced with asingle cannula design. As shown in FIGS. 12A-12B, a single cannula 470extends through the housing 412 wherein the single cannula 470 includesa lumen extending therethrough, a first end comprising the patientpuncture tip, a second end comprising the non-patient puncture tip, andan opening 444 through the cannula 470 into the lumen at a locationbetween the first end and the second end providing fluid communicationbetween the lumen of the cannula 470 and the first chamber 426 of thehousing.

With continuing reference to FIGS. 12A-12B, the porous vent 910 can bereplaced with the porous vent 920 of the invention, including theblocking member 925, and can be used in this needle assembly 410. Thisneedle assembly 410 has a housing design 412 wherein the first end 414of the housing comprises an elongate longitudinal first portion 419having a first diameter and the second end of the housing 416 comprisesa second portion 421 having a second diameter larger than the firstdiameter of the first portion 419. In this manner, the first portion 419of the housing 412 essentially defines the flashback or first chamber426, and the second portion 421 of the housing 412 essentially definesthe secondary chamber 427. The porous vent 920 of the invention may bepositioned within the interior of housing 412 at a location spanning thetransition between the first diameter of first portion 419 and thesecond diameter of second portion 421. The porous vent 920 including theblocking member 925 of the invention causes the fluid to flow along acontrolled longitudinal path from the first end face 930 to one of thecentral location 934 and the second end face 932 and subsequentlythrough a central aperture 428 opening between the first chamber 426 andthe second chamber 427.

Referring now to FIGS. 22A-22D, the porous vent 920 a, 920 b, 920 c, and920 d, may be used in needle assemblies to separate the first chamber626 a, 626 b, 626 c, and 626 d from the second chamber 627 a, 627 b, 627c, and 627 d wherein the fluid flows through the first or second endface. In particular, as shown in FIG. 22A, the second end face 932 a ofthe porous vent 920 a is blocked such that fluid flows from the firstchamber 626 a to the back end of interior cylindrical wall 624 a andfrom this second end face 932 a, through the porous vent 920 a and exitsthrough the first end face 930 a into the second chamber 627 a. In FIG.22A, the housing 612 a includes a cylindrical interior wall portion 628a which extends into the axial hole of the porous vent 920 a in anabutting relationship with respect to the inside surface 938 a of theporous vent 920 a. This cylindrical portion 628 a functions as theblocking member to control the fluid flow within the porous vent 920 a.In FIGS. 22B-22D, the fluid flows from the first end face 930 b, 930 c,930 d along a longitudinal path to the second end face 932 b, 932 c, 932d and exits through this second end face into the second chamber 627 b,627 c, 627 d.

In the designs shown in FIGS. 22B-22D, the housing 612 b, 612; 612 dincludes a rear hub 680 b, 680 c, 680 d having a cylindrical portion 682b, 682 c, 682 d in an abutting relationship with respect to the insidesurface 938 b, 938 c, 938 d of the porous vent 920 b, 920 c, 920 d. Thiscylindrical portion 682 b, 682 c, 682 d functions as the blocking memberto control the fluid flow within the porous vent 920 b, 920 c, 920 d.

Referring now to FIGS. 23A-23B there is shown a needle assembly,generally indicated as 710 comprising a housing 712 defining a housinginterior 720. The housing comprises at least one cannula 732 having apatient puncture tip 738 extending from a first fluid inlet end 714 ofthe housing 712 and a non-patient puncture tip 762 extending from asecond fluid outlet end 716 of the housing 712. The non-patient puncturetip 762 and the patient puncture tip 738 are in fluid communication witheach other within the housing interior 720. The porous vent 920 ispositioned within the housing interior 720 separating the housinginterior into a first chamber 726 and a second chamber 727. The porousvent includes pores for passage of fluid therethrough from the firstchamber 726 to the second chamber 727 and the porous vent 920 isconfigured to control flow of the fluid such that the fluid flows in anaxial direction through the vent. In this design, the housing 712includes a rear hub 780 having a cylindrical portion 782 extendingtherefrom and into the first chamber 726 toward the first end 714 of thehousing 712 to define a portion of the first chamber 726. The solecommunication path between the housing interior 720 and the externalenvironment is via the patient puncture tip 738. As discussed in detailabove, the porous vent 920 comprises a tubular member having a first endface 930, a second end face 932, and a central portion 934 extendingbetween the first end face 930 and the second end face 932. The tubularmember includes an axial hole 936, as shown in FIGS. 18, 19, and 23B,configured for surrounding at least a portion of the cylindrical portion782 extending from the rear hub 780. The at least one cannula 732 islocated within at least a portion of the cylindrical portion 782. Thecylindrical portion 782 extends into the porous vent 920 and abutsagainst the inside surface 938, as shown in FIGS. 18, 19, and 23B, ofthe porous vent 920. This cylindrical portion 782 functions as theblocking member 925 to control the flow of fluid such that it flowsalong a controlled longitudinal path and subsequently through a centralaperture opening 628 between the first chamber 726 and the secondchamber 727. In the design shown in FIGS. 23A-23B, the rear hub 780 andthe cylindrical portion 782 extending therefrom also block the secondend face 932 of the porous vent 920 to prevent fluid flow through thesecond end face 932.

According to an alternative design, as shown in FIG. 24, the rear hub780 a can include a tapered cylindrical member 782 a which extends intothe first chamber 726 toward the first end 714 of the housing 712 todefine a portion of the first chamber 726. Fluid, in the form of liquidand air enters into the porous vent 920 from the first end face 930,flows along a longitudinal path therethrough due to the presence ofblocking member 925, and exits into the second chamber 727 through thesecond end face 932.

It can be appreciated that the needle assemblies shown in FIGS. 22A-22D,23A-23B, and 24 can be used with the single cannula design, as describedabove in relation to FIGS. 12A-12B, or with a pair of cannulas includinga gap between the interior blunt ends as described above in relation toFIGS. 13A-13C.

The blocking member 925 can be formed from a variety of methods and/ordevices as discussed in detail above, such as from a bushingpress-fitted into the inside surface of the porous vent, an adhesivelocated between an inside surface of the porous vent and an outerdiameter surface of the cylindrical member 782, 782 a, a fused innersurface portion of the porous vent 920, a separate member, such as aplastic member or a wall portion of the housing in abutting relationshipwith respect to the inside surface of the porous vent, or any otherpreviously disclosed techniques for rendering a portion of the porousvent non-porous to control the axial flow of the fluid therethrough andto reduce random radial movement of the fluid.

The porous vent and blocking member of the present invention causing thefluid to flow along a controlled path through the porous vent along thelongest path, depending upon the shape of the porous vent, results inslower decay of vacuum within the second chamber of the needle assemblyeven after multiple tube draws, reduced pooling of blood into the secondchamber, and reduced blood droplet occurrences.

FIG. 25 shows a cross-sectional view of the needle assembly of theinvention including the blocking member of the invention and showinganother embodiment of the controlled flow of fluid along the longestpath through the porous vent 920 wherein the longest path is in a radialdirection. The needle assembly, generally indicated as 1010, includes ahousing 1012 having a fluid inlet end or first end 1014 and a fluidoutlet end or second end 1016. Needle assembly 1010 includes exteriorwall 1018 defining the housing interior. Exterior wall 1018 extendsgenerally longitudinally at the first end 1014 forming an elongatelongitudinal first portion 1019 having a first diameter. At second end1016, exterior wall 1018 forms a second portion 1021 that has a seconddiameter that is generally larger than the first diameter of the firstportion 1019. First portion 1019 and second portion 1021 may be arrangedrelative to each other in a variety of arrangements, so long as they arecapable of functioning for transport of air therebetween as discussedherein. Needle assembly 1010 further includes a fluid inlet cannula 1036extending from first end 1014 of housing 1012. Fluid inlet cannula 1036includes an exterior end 1042 that defines a first puncture tip such asa sharpened bevel at patient puncture tip 1038, and extends within firstend 1014 of housing 1012 and may be fixedly mounted therein. Fluid inletcannula 1036 is characterized further by a substantially cylindricallumen extending between the ends and communicating with the interior ofhousing 1012.

Needle assembly 1010 also includes a second puncture tip such asnon-patient puncture tip 1062 extending from second end 1016 of housing1012. Fluid outlet cannula 1052 extends within second end 1016 ofhousing 1012, and may be fixedly mounted therein. Fluid outlet cannula1052 is characterized further by a substantially cylindrical lumencommunicating with the interior of housing 1012. Outlet cannula 1052 ismounted within housing 1012 so that an interior end 1064 passessubstantially coaxially therein such that outlet cannula 1052substantially aligns axially with the interior end of inlet cannula1036. The interior end 1064 of outlet cannula 1052 is spaced only asmall distance from the interior end 1039 of inlet cannula 1036, therebyforming an axial gap therebetween for flow of blood into flashbackchamber 1026 about outlet cannula 1052.

The porous vent 920 of FIG. 25 is washer-shaped, such that the longestpath extends in the radial direction. The first face 930 and second face932 of porous vent 920 are arranged to abut inside surfaces of firstportion 1019 and second portion 1021. The first portion 1019 and secondportion 1021 abutting the porous vent function as the blocking member tocontrol the flow of the fluid (blood and air) such that it moves alongthe longest path, which is in a controlled radial direction from aninner portion of the porous vent to the outer circumferential endsurface 933 of the porous vent 920, and out into secondary chamber 1027.

The relative dimensional calculations, volumes and pressures apply toboth illustrated and unillustrated embodiments of the invention.Accordingly, the scope of the invention as defined by the appendingclaims is not limited to the specific illustrated embodiments. Variousother changes and modifications may be effected therein by one skilledin the art without departing from the scope or spirit of the invention,and it is intended to claim all such changes and modifications as fallwithin the scope of the invention.

What is claimed is:
 1. A needle assembly comprising: a housing defininga housing interior, said housing comprising at least one cannula havinga patient puncture tip extending from a first end of the housing and anon-patient puncture tip extending from a second end of the housing, thenon-patient puncture tip and the patient puncture tip being in fluidcommunication with each other within the housing interior; and a porousvent positioned within the housing interior separating the housinginterior into a first chamber and a second chamber, the porous ventincluding pores for passage of fluid therethrough from the first chamberto the second chamber, said porous vent including a blocking member tocontrol flow of the fluid such that the fluid flows in an axialdirection through the porous vent, wherein the housing includes a rearhub having a cylindrical portion extending therefrom and into the firstchamber toward the first end of the housing to define a portion of thefirst chamber, said cylindrical portion forming at least a portion ofthe blocking member, and wherein the sole communication path between thehousing interior and the external environment is via the patientpuncture tip.
 2. The needle assembly of claim 1, wherein the porous ventcomprises a tubular member having a first end face, a second end face,and a central portion extending between the first end face and thesecond end face, the tubular member including an axial hole configuredfor surrounding at least a portion of the cylindrical portion extendingfrom the rear hub, said at least one cannula being located within atleast a portion of the cylindrical portion.
 3. The needle assembly ofclaim 2, wherein the blocking member renders a portion of the ventnon-porous to cause said fluid to flow along a controlled longitudinalpath and subsequently through either a central aperture opening betweenthe first chamber and the second chamber or through one of the first endface or the second end face.
 4. The needle assembly of claim 3, whereinthe rear hub and the cylindrical portion extending therefrom block thesecond end face of the porous vent to prevent fluid flow through thesecond end face.
 5. The needle assembly of claim 3, wherein the blockingmember comprises the cylindrical portion extending from the rear hub,said cylindrical portion being located adjacent to an inside surface ofthe porous vent.